Wear adjusting device for disk brakes and method for controlling the device

ABSTRACT

The invention relates to a wear adjusting device for a motor vehicle disk brake and a method for controlling the device. A brake actuated rotating lever primarily effects a slidable element which actuates at least one adjusting spindle. The spindle presses a brake lining in the direction of a brake disk. According to the invention, the adjustment device consists of an electric drive which adjusts at least one of the adjusting spindles through rotary operation.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a wear adjusting device for disk brakes as wellas to a method for controlling a wear adjusting device.

A wear adjusting device for pneumatically operated desk brakes is known,for example, from International Patent Document WO 91/19115. The diskbrake according to International Patent Document WO 91/19115 having anapplication device on one side contains a cam lever which is rotatableabout an axis parallel to the brake disk plane and preferably interactsby way of a traverse with one or two adjusting spindle(s) against whicha brake lining is supported. The two adjusting spindles are coupled by abelt or a chain. A rotary drive, which can be driven by the cam lever,projects into a recess of the one adjusting spindle and, during thecontact stroke causes a screwed connection of the adjusting spindle—andthus, by way of the toothed belt, also of the second adjustingspindle—in the approaching direction with the brake disk. The rotarydrive contains a one-way rotary clutch as well as a torque-limiting oroverload clutch by means of which an unintentional screwed connection ofthe adjusting spindles is avoided during the stall stroke and therelease stroke.

Important elements of the above-mentioned brake adjustment are theone-way clutch and the overload clutch which are designed, for example,as systems operating in a frictionally engaged manner. For example, theone-way clutch operates as a wrap spring one-way clutch and the overloadclutch operates as a friction slipping clutch or as an axial dentureclutch. International Patent Document WO 91/19115 illustrates, forexample, in FIG. 5 that the overload clutch is constructed in the rollerbearing technology as a ball coupling whose shifting moment is causedexclusively by the geometry of the ramp-shaped pockets receiving theballs and by the extent of the prestressing force. This system has theadvantages of being virtually free of frictional influences andpermitting very high shifting moments in a small space. The one-wayclutch of this embodiment is implemented as a grip roller clampingone-way clutch which has a very high response precision and permits theimplementation of very high transmission moments in a small space.

The above-described adjusting device has had good results per se butrequires several high-precision parts and therefore represents an objectof the efforts of searching for further possibilities for lowering themanufacturing costs of pneumatic disk brakes.

Another adjusting device as well as a method for operating a vehiclebrake is disclosed in German Patent Document DE 195 21 401 C1corresponding to U.S. Pat. No. 5,568,845. It is a disadvantage in thiscase that, for overcoming the easing play by the adjusting device, theoperating time or reaction time of the brake is increased. The presentinvention relates to the described problems and provides an adjustingdevice which, in industrial-scale manufacturing, permits a clearreduction of cost in comparison to the above-described system. Thecharacteristics of the solution are preferably a—particularlyelectronically commutated—direct-current geared motor or possibly astepping motor is arranged in the brake-integrated control unit suchthat the transmission output element acts in the sense of a rotaryoperation onto the wear adjusting mechanism of the brake.

Although disk brakes operated by electric motors have been known for along time, because of the numerous problems with respect to theirimplementation (cost, resistance to failure, etc.), they have not beensuccess in practice. The invention uses a different approach in that itremains with the concept of a pneumatically applied disk brake and onlythe adjusting of the brake is carried out by an electric drive. Thus,the invention ideally combines the advantages of a pneumaticallyoperated disk brake (safety, reliability) with the advantages of anelectric drive (low cost). In addition, by means of an electric drive,the response time is reduced during the adjusting of the brake; therequired easing play can be reduced to a very low value as a result ofthe adjustment between brake operations according to the invetion; andthe air consumption (for example, the emergy consumption connected withgenerating the air) of the pneumatic system is reduced.

In the case of two-spindle brakes, the intervention preferably takesplace upon the synchronization mechanism (such as a chain). In the caseof single-spindle brakes, it takes place preferably directly upon thewear adjusting element (adjusting spindle).

Advantageous further developments of the invention are contained in thesubclaims.

The invention also solves the problem of operating anelectric-motor-driven adjusting device for a pneumatically operatedbrake in a manner which is as simple and reliable as possible. Thecharacteristics for solving this problem are the following sequence ofsteps:

Step A: Immediately after complete reduction of the operating pressurein the brake cylinder preferably a pneum another adjusting movement ofthe adjusting spindles is carried out which is dimensioned such that acomplete elimination of the easing play is achieved.

Step B: Then the adjusting mechanism (the adjusting spindles) are setback by the electric drive by a defined amount which corresponds to agiven desired easing play.

This type of adjustment has the following advantages: Since, when thebrake is operated, the easing play is conventionally overcome by therotary lever, the eccentric traverse and the piston, the response timeof the brake is shortened. The required brake cylinder stroke and thusalso the consumption of pressure energy is reduced because of the lowrequired easing play which is adjusted exclusively between two brakeoperations. Since, after each operation of the brake, the easing play isnewly adjusted in a precise manner, a very uniform easing play is, inaddition, obtained under all operating conditions. In the event of aservicing, considerable time is saved because of the fact that allbrakes of the vehicle can automatically be moved into the servicingposition for the exchange of the brake lining and the easing playadjustment after the termination of the servicing also takes placeautomatically.

After each operation of the brake, the wear adjusting mechanism istriggered in the sense of an application until the easing playapproaches zero. Subsequently, the adjusting mechanism is set back byway of the motor operator by a given amount which corresponds to thedesired easing play. Thus, after the reduction of the operating pressureof the brake cylinder, an operating pulse is given in the sense of anapplication which is so long that a complete elimination of the easingplay is achieved. Immediately following this application pulse, thesetting back will then take place to the required desired easing play.

As an alternative for reducing the operating frequency of the adjustingmechanism, the above-described sequence may in each case only take placeafter a given number of brake operations.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectional view of a disk brake with an embodimentof an adjusting device according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The construction and function of the pneumatic disk brake according toFIG. 1 will be outlined first. The disk brake 1 has a caliper 2 whichreaches around an internally ventilated brake disk 3. On one side of thebrake disk 3, an application device 4 is provided which has a slidinglydisposed operating rotary lever 5 which is moved by a piston rod of acompressed-air cylinder (not shown) and, in turn, operates or rotates aneccentric 6 which, in turn, by way of displaceable element, also knownas a pressure piece traverse 7 interacts with two adjusting spindles 8,9 against which one of the brake linings or shoes 10 is supported. Thetwo adjusting spindles 8, 9 can be coupled and synchronized, forexample, also by a chain (not shown). A spring is tensioned between thetraverse element 7 and the caliper 2 and thus provides a pretensioningof the traverse element 7 in the direction of the rotary lever 5. Thedetails are shown in the aforementioned U.S. Pat. No. 5,568,845.

On both exterior sides, the traverse element 7 has one bore respectivelywhich is provided with an internal thread and into which bore theadjusting spindles 8 and 9 are screwed which are provided with externalthreads. Rotary drives 11, which are each driven directly by electricmotors 12 and cannot be rotated relative to the spindles 8, 9, projectinto the recess of the adjusting spindles 8, 9.

When the brake is acted upon by compressed air, the rotary lever 5 isswiveled, which rotates the eccentric 6 and displaces the traverseelement 7 in the direction of the brake disk 3, so that the spindles 8,9 move in the direction of one lining 10. In the process, the caliper 2axially displaceably disposed on a brake support S is also displaced andtakes along the other brake lining 10 so that the brake is applied.

In the following, the function of the electric drive of the wearadjusting device according to the invention will now be described.

After each operation of the brake 1, after the reduction of the brakecylinder application pressure, one electric motor 12 is triggered in thesense of an application of the adjusting mechanism (step A). By way ofthe motor 12 and the rotary drive 11 and the synchronizing mechanism,the spindles 8, 9 are moved so far in the direction of the brake shoes10 that, when the brake is released, the easing play approaches zero.After a complete pressure compensation has taken place at the operatingpiston of the brake, the electric motor 12 is then (according to acorrespondingly dimensioned control formula) moved so far into therelease direction that a defined easing play is achieved between thebrake shoes 10 and the brake disk 3.

The above-described method is particularly advantageous, among otherthings, because it does not require additional sensor elements whichwould undesirably increase the costs of the adjusting device.

According to the variant of FIG. 1, each of the spindles 8, 9 has one ofthe electric motor operators 12 which, when an easing play path isexceeded, adjust the two adjusting spindles individually. In this case,by means of a corresponding analyzing logic in the electric brake system(for example, in the form of a supplementary software to the antilocksystem or the EBS control unit), the lining wear in general and apossibly occurring diagonal brake lining wear can be monitored andpossibly corrected. Furthermore, it is advantageous to integrate theelectric control an/or supply lines 14 into the closing lid 13, so that,when the lid is mounted, the required connections are also alreadyinstalled.

What is claimed is:
 1. A wear adjusting system for a pneumaticallyoperated disk brake including a pneumatic actuator, the wear adjustingsystem comprising: a) a rotary lever operating upon at least onedisplaceable element which operates at least two adjusting spindles,which press a brake lining in the direction of a brake disk duringbraking by the pneumatic actuator; b) an adjusting device, coupled tothe adjusting spindles and adjusts the adjusting spindles by a continuedrotation; c) a synchronization mechanism synchronizing the adjustingmovements of the adjusting spindles; and d) the adjusting device has anelectric drive coupled to the synchronization mechanism to rotatinglyadjust the two adjusting spindles.
 2. A wear adjusting system for apneumatically operated disk brake comprising: a) a rotary leveroperating upon at least one displaceable element which operates anadjusting spindle which presses a brake lining in the direction of apneumatic brake disk during braking; b) an adjusting device coupled tothe adjusting spindles and adjusts the adjusting spindles by a continuedrotation; and c) the adjusting device has an electric drive coupleddirectly to the adjusting spindles to rotatingly adjust the adjustingspindle.
 3. A wear adjusting device according to claim 1, wherein theelectric drive is a commutated direct-current geared motor.
 4. A wearadjusting device according to claim 1, wherein one or more electriccontrol and supply lines are integrated in a closing lid of the diskbrake.
 5. A method for controlling a lining wear adjusting device apneumatic disk brake having a pneumatic cylinder for applying andreleasing the brakes and an electric drive for adjusting spindles, themethod comprising: completely reducing operating pressure in the brakecylinder; adjusting movement of at least one of the adjusting spindlessuch that a complete elimination of easing play is achieved; and settingback the adjusting spindle by the electric drive by a given amount whichcorresponds to a defined desired easing play.
 6. A method according toclaim 5, further comprising the steps of coupling a rotary lever to thebrake cylinder; and positioning the rotary lever to operate upon atleast one displaceable element which operates at least one adjustingspindle, which press a brake lining toward a brake disk during braking;and actuating the electric drive to rotatingly adjust the at least oneadjusting spindle.
 7. A method according to claim 5, further comprisingthe step of adjusting the adjusting spindle when a given number of brakeoperations has been reached.
 8. A method according to claim 5, whereinlining wear is monitored and corrected.
 9. A method according to claim5, wherein the brake includes two adjusting spindles; and diagonal wearis monitored and corrected using the adjusting spindles.